1. Field of the Invention
This invention relates to a sliding or movable stopper or a piston of a syringe used for the hypodermic injection of liquid medicaments.
2. Description of the Prior Art
Syringes and generally constructed of a barrel and a plunger of glass slidably combined and of a barrel are a plunger rod provided, at the end thereof, with an elastic body of a rubber or thermoplastic elastomer, as a sealant, the barrel and plunger rod being of a resin such as polyethylene, polypropylene or polycarbonate. At the present time, this combination of a barrel and a sliding stopper consisting of a resin and rubber elastic body have most widely been used in the world. Of late, a syringe additionally serving as a container for a medicament has frequently been used in which the medicament is previously charged and sealed by a sliding stopper of a rubber elastic body.
For the purpose of preventing a medicament in a syringe from deterioration of the quality thereof due to a slidable stopper, there have been proposed a slidable stopper with a part, in contact with a liquid medicament, coated with a thin film of a fluoro-resin (Japanese Utility Model Publication No. 19435/1977), a sliding stopper consisting of a rubber laminated with polyethylene (hereinafter referred to as PE) or polypropylene (hereinafter referred to as PP) (Japanese Utility Model Publication No. 32602/1980) and a slidable stopper partly laminated with a fluoro-resin film (German Patent No. 3345351 A1). In any case, these proposals are directed to improvement of the chemical resistance of the stopper of a rubber elastic body and do not take the sliding property of the stopper into consideration.
Therefore, the sliding property of a rubber-like elastic body stopper is maintained by coating the inner wall of a barrel of a syringe and the stopper with s suitable quantity of silicone oil and silicone oil-free syringes for medicaments have not been available in the market.